(1) Field of the Invention
This invention relates to a device for the collecting and dispensing of non-pressurized liquids, such as puddled liquids or those in an open container. In the case of blood, the preferred liquid for collection, the device is particularly suited to collect from a non-venous source, such as blood drops drawn by a pin prick.
(2) State of the Prior Art
Of the many devices available to provide blood serum for analysis, the one which has become the norm is the evacuated container. This is simply a partially evacuated glass tube openable at one end except for a septum placed there. One improvement over such an evacuated container which is particularly useful comprises such a glass tube with a movable plug contained within the tube. The plug is preferably a silica gel, with or without a plastic cup-like mandrel positioned with its open end pointed to the septum. By reason of the vacuum, collected blood is easily drawn into the container. The container is then spun about a centrifuge axis adjacent to the septum end, and the gel by reason of its selected specific gravity works up to the serum-cell interface where it plugs the container against remixing of the serum and cells. An example of such a container but without the mandrel is shown in U.S. Pat. No. 3,852,194.
Although such a device is useful in separating the serum from the cells, it has not avoided the transfer difficulties by which the separated serum is obtained. That is, after centrifuging, the serum is commonly poured off into yet another container for the desired clinical testing. All such transfer operations are time consuming, requiring either hand processing or complicated, expensive automatic handling. Furthermore, whenever there is a transfer of a liquid sample to a separate, open container, the sample is aerated and CO.sub.2 loss or gain can occur. There is also the danger of improper transfer, either by the use of the wrong container, by the improper patient labeling of the new container, or by both. Still further, contamination of the serum by foreign materials can occur, including for example, contamination by blood cells collected at the septum-container interface prior to centrifuging, a condition known as "blood-ring contamination".
Still other drawbacks concerning evacuated containers are that the rapid intake tends to cause hemolysis by reason of the high shear rate, particularly when flow is through reduced diameters; the vacuum can cause collapse of the patient's vein; and occasionally the containers become "flat", i.e., they lose their vacuum. In such a case of a "flat" container, the broken seal is generally insufficient to create a truly vented configuration, so that the hydrostatic pressure of the veins from which the blood is drawn encounters back pressure, and the rate of fill is insufficient. When the container is formed from solid glass, it is not possible prior to actual use to determine the loss of vacuum merely by visual inspection, and the result is that the patient has to wait while the technician looks for a new, hopefully evacuated, container.
Yet another disadvantage of such evacuated containers is that they are generally used to collect relatively large volumes, on the order of about 5-10 ml. Since the serum and cells are separated within this volume by centrifuging, a small fraction cannot be efficiently collected. However, certain classes of patients cannot spare this amount of blood, including both the elderly and the infant. To deal with this problem, simple capillary draws have been used on pin pricks. Dispensing of serum from such draws is difficult, however. Furthermore, a device capable of collecting blood volumes intermediate the minimum amount typified by capillary draws and the large amount by evacuated containers is desirable.
As a means of collecting intermediate amounts, a capillary tube has been connected to a larger container of the type shown, for example, in U.S. Pat. No. 3,640,267. These devices do provide a reduced volume collection, such as for the elderly. Although the U.S. Pat. No. 3,640,267 provides for non-venous collection devices, such devices are not suitable for serum separation in the same container. Furthermore, such devices use a collapsible membrane which requires the operator to repeatedly actuate the device. A preferred construction is one in which no operator effort needs to be expended.
U.S. Pat. No. 3,645,252 also discloses a device to collect more than the minimum amount, but less than the collection capacity of evacuated containers. However, vacuum again is resorted to in such devices, and the utility is stated to be for venous sources, rather than non-venous.
Yet another disadvantage with conventional capillary draws is that, conventionally, serum is removed therefrom only after phase separation is complete, and then by pressurization or vacuum aspiration, as shown for example in U.S. Pat. No. 3,763,705. Such techniques tend to disturb the interface of the phase separation. Any device which disposes serum for dispensing outside of the capillary passageway as a part of the phase separation step would both reduce the number of processing steps and avoid disturbing the interface.
A vented, non-venous collection device has been disclosed, for example, in U.S. Pat. No. 3,926,521 issued Dec. 16, 1975, which uses a capillary tube connected by a frangible, tapered neck to a tube suitable for centrifugal blood separation. However, the capillary passageway terminates at the neck, so that only by positioning the device below the pooled blood can blood continue to flow by gravity into the device to fill it. The device cannot be located above the source.
Mild obstructions have been placed in blood collecting devices for various purposes other than for creating a capillary effect at the obstruction to fill the container. For example, the pipette shown in U.S. Pat. No. 3,741,732 has capillary flow along its entire length, and the obstruction by its hydrophobic nature is designed to terminate rather than assist flow. However, the entire contents are to be dispensed at once, so that no separate dispensing chamber or means for displacing liquid into the chamber are provided for.
In the syringe disclosed in U.S. Pat. No. 2,941,869, a coiled wire is disposed in a tube solely to hemolyze the blood flowing past it. Nowhere is capillary flow discussed.
Blood flow devices having capillary restrictions at a portion intermediate the ends thereof have been constructed not for the purpose of collecting blood and for separating serum, but rather for blood cell counting, as shown for example, in U.S. Pat. Nos. 2,369,577; 2,779,232; 2,807,416 and 2,875,666. These devices are not intended for, nor are they capable of, use as non-pressurized serum collectors and separators as there is no provision, for example, for capillary flow extending the entire sample collection length.
Flexible containers have been used to collect whole blood, and by reason of their flexibility, they may have capillary passageways somewhere defined when the walls are collapsed. However, the collapsed wall condition is designed not to fill the containers by capillary action, but rather either to create a vacuum which causes filling of the container, as shown for example, in U.S. Pat. No. 3,513,829, or to indicate whether desired arterial blood as opposed to undesired venous blood is being collected, as shown for example in U.S. Pat. No. 3,785,367.
U.S. Pat. No. 3,867,923 is representative of blood collection bags which are completely collapsed along their entire length, and which therefore initially provide a capillary passageway along their entire length. However, such devices lose their effective capillary as soon as blood enters. Because they are not vented to the atmosphere, they require the patient's blood pressure to exepnd the device into its full volume. They cannot be used to collect non-pressurized blood.
Patents relating generally to the background of blood collection include for example U.S. Pat. No. 3,610,226.
(3) Related Applications
In U.S. application Ser. No. 545,670, filed on Jan. 30, 1975, entitled "Metering Apparatus", now abandoned and refiled and issued as U.S. Pat. No. 4,041,995, there is disclosed a dispenser chamber uniquely designed to dispense microvolume drops, one at a time, of fluids of variable properties such as blood serum. In U.S. Pat. No. 4,012,325 issued on application Ser. No. 581,345, filed on May 27, 1975, a CIP of application Ser. No. 539,577, filed on Jan. 8, 1975, now abandoned, entitled "Biological Fluid Dispenser and Separator", there is disclosed a combined serum separator and dispenser which preferably draws in blood at one end and collects and dispenses drops of serum at the other, whereby blood ring contamination can be avoided. The device can be vented or evacuated.
In U.S. Pat. No. 4,052,320 issued on Oct. 4, 1977 on commonly owned U.S. application Ser. No. 703,476, filed on July 8, 1976, a continuation-in-part application of Ser. No. 609,121 filed on Aug. 29, 1975 by R. F. Jakubowicz, entitled "Telescoping Serum Separator and Dispenser", there is disclosed a combined serum separator and dispenser wherein the dispensing chamber telescopes with respect to the serum separating compartment to open or close flow of serum from the separating compartment to the dispensing chamber.
In U.S. application Ser. No. 658,208, filed on Feb. 17, 1976, and now U.S. Pat. No. 4,091,182, entitled "Vented Liquid Collection Device", there is disclosed a vented collecting and dispensing device which uses a capillary passageway along a portion of the sample collection length of the collection compartment to increase the speed of collection. The prime mover of the blood in such a device is the veinal pressure of the patient.